Censorship can be explicit, as in laws passed to prevent information being published or propagated (as in Australia or China where certain internet pages are not permitted entry), or it can take the form of intimidation by government or even by popular censure, where people are afraid to express or support certain opinions for fear of losing their lives, or their jobs, position in society, or in academia, their academic credibility. In this latter, form it is sometimes called McCarthyism.
Censorship is generally rampant in dictatorships and other authoritarian nations. Democratic nations usually have far less institutionalized censorship, and instead tout the importance of freedom of speech.
Some thinkers include as censorship other attempts to suppress points of view or ideas such as propaganda, media manipulation, spin (politics), or disinformation. These methods, collectively, tend to work by refusing the ideas a receptive audience.
Others point out the suppression of access to the means of dissemination of ideas by governmental bodies such as the FCC in the United States of America, or by a newspaper that refuses to run commentary the publisher disagrees with, or a lecture hall that refuses to rent itself out to a particular speaker. Thinkers such as philosopher and novelist Ayn Rand consider this latter form of censorship to be an acceptable outcome of the defense of property rights. Contradictions of her position emerge from her disapproval of state backed monopoly license in the arena of radio and telecommunication broadcast and state funding of the arts.
Data havens and decentralized peer-to-peer file sharing systems such as Freenet can be used to prevent censorship.
See also:
Analysis of censorship in action
List of banned works